FIG. 8 shows a conventional device of pulse width modulation type for load drive, and FIG. 9 shows drive timings used by the device of pulse width modulation type for load drive.
A driving section 100 is composed of a drive timing generator 101, a first output unit 102, and a second output unit 103 to drive a load 104 on the basis of an analog drive input signal A shown in FIG. 9.
The drive timing generator 101 outputs a drive timing signal B and a drive timing signal C both shown in FIG. 9, on the basis of the level of a drive input signal A. The drive timing signals B and C, obtained by modulating the pulse width of the drive input signal A, are subjected to level conversion by the first and second output units 102 and 103, respectively. The resulting output signals D and E are applied to one end and the other end of the load 104, respectively. Consequently, current flows through the load 104 during a differential voltage interval t1. . . as shown in FIG. 9.
Specifically, as shown in FIG. 9, the voltage value of the drive input signal A is captured into the drive timing generator 101 at any timing. If the voltage value of the drive input signal A is greater than that of a reference voltage, the drive timing generator 101 generates the drive timing signals B and C so as to increase the width of an interval during which the level of the first output signal D increases above the level of the second output signal E consistently with the absolute value of the amount of the differential voltage between the voltage of the drive input signal A and the reference voltage so that current flows through the load 104 from an output of the first output unit 102 toward an output of the second output unit 103. The drive timing generator 101 thus controls the differential component between the output signals D and E (two pulse-like output signals in respective phases) output by the first and second output units 102 and 103 to drive the load 104.
If the voltage value of the drive input signal A is smaller than that of the reference voltage, the drive timing generator 101 generates the drive timing signals B and C so as to increase the width of an interval during which the level of the second output signal E increases above the level of the first output signal D consistently with the absolute value of the amount of the differential voltage between the voltage of the drive input signal A and the reference voltage so that current flows through the load 104 from the output of the second output unit 103 toward the output of the first output unit 102. The drive timing generator 101 thus controls the differential component between the output signals D and E (two pulse-like output signals in respective phases) output by the first and second output units 102 and 103 to drive the load 104.
If the voltage value of the drive input signal A is equal to that of the reference voltage, the drive timing generator 101 generates the drive timing signals B and C so that the level of the first output signal D equals that of the second output signal E. The drive timing generator 101 thus controls the differential component between the output signals D and E (two pulse-like output signals in respective phases) output by the first and second output units 102 and 103 to drive the load 104.